LRR (low rolling resistance) tires - Green Seal report & list
 

For those considering replacing their tires with a LRR versions, this report is a good place to start for general info. It's getting long in the tooth (1993), but the basics still apply.

• 1.5 to 4.5% of total gasoline use could be saved if all replacement tires in use had low rolling resistance

• About 237 million replacement tires are sold in the U.S. each year – none has rolling resistance labeling

• This report presents previously unpublished data on leading tires with low rolling resistance

Report (PDF): Green Seal's Choose Green Report: Low Rolling Resistance Tires

Excellent Report
 

This is a great report -- I used it to purchase my latest set of treads. I attribute a decent percentage increase to my over-inflated LRR's.

For more up-to-date info, Consumer Reports has rolling resistance data in their tire reviews. The problem is that it requires an online subscription to the site or the magazine. You may be able to check your local library and locate a hard-copy for reference -- but those are the only references that I've been able to find actual testing on this subject.

RH77

I saw the Consumer Reports report in late 2006. It rated rolling resistance the same way that it rates everything else, with the red dot / black dot system. There were no actual LRR numbers. At the top of the list in 2006 was the Michelin Energy MXV and just under that was the Michelin Harmony. I bought the Kumho A/S 795's for the Prius which ranked just below the Michelins, but were 1/2 to 1/4 of the price. The sidewall max is 35 PPSI but I have been running them at 50-55 PSI. 40k miles so far and easily another 40k in them.

Hopefully the 2007 report had actual LRR values in it. If so, I would go to the library to see it.

With California's July '08 implementation of LRR labeling & standards, I'd expect it's going to get easier for the public to get info & make judgements than it has been.

My car's tires are more likely to dry rot off the rims before I ever wear them out, so eventually I'll have to shop for replacements too :P

FYI that report is from 2003

The most comprehensive List I could find was (still old from 2005)
http://onlinepubs.trb.org/onlinepubs...tance_Data.pdf

http://forum.ecomodder.com/showthread.php?t=466

not to grave dig, but I'm going to shop for some Low rolling resistance tires and was wondering what the best choice is as of right now...

Maybe there's a newer chart out now?

is there a more updated source?

Even if there is an up to date study, those tires mentioned are still awesome to look into. Just looked at the top of the line Bridgestone B381's and they are going for about 90 bucks a piece. Steep price, but they are the best on the original study.
.02

Here's some new info in an easy to read source ---> Low-rolling resistance tires - Wikipedia, the free encyclopedia
:D

I just bought 2 new Michelin Energy Saver Tuesday. The bad news is they were pumped at 23 :mad: lower than the minimal placard (33) so I pumped them up to 46 this morning :)

After a little search I found that :
Sommerreifen 195/65 R 15 V (2008) - Tabelle
Sorry, it's in German... Thanks to babelfish :
I don't know how they did their tests. The french forum in which I found the link was saying that my tires have a very good note except for breaking on wet grounds, so they are "recommendable" and not "particularly recommendable".

Denis.

According to Michelin themselves, the new HydroEdge is better than the Harmony. They won't tell me how either compares to the MXV4 Plus that I have on another car. Some blah-blah-blah about different speed ratings classes.

Hi,

This is the biggest load of crap in the tire sales business. Especially with women customers, they try to brow beat us into buying a tire "speed rated" at 150mph rather than one "only" rated for 120mph...sheesh.

Hi,

Newbie here, so sifting through old muck on the site...

How do you think hyperinflation would affect the 'speed ratings' that the company puts on the tyres?

If most energy losses happen due to hysterisis, as heard earlier on the forum, it should be affected severely because now the tyre does not flex much, so hysterisis losses would go down. So, if I get it right, a lower speed rated tyre would hold up to higher speeds (for a comparable energy loss, hence heat buildup) - quite an unintended consequence of hyperinflation...

Maybe I am mixing two issues up, but it certainly would bring clarity to an issue that vexes us each time visiting that tyre shop...

Makes sense to me.
But if I were going to be driving at 90 or 120 mph instead of max 60-75, I'd want to make darn certain the tire was up to whatever I'm doing to it.

Clarifying a few points
 

1) In addition to the Green Seal report being quite old (2003), the report also does not account for the different tire sizes. The rolling resistance of otherwise identical tires varies according to tire size - as does rolling resistance coefficient.

The tire size vs rolling resistance (and rolling resistance coefficient) of tires has not been explored enough to be able to predict the RR (or RRC) from a single, but different, tire size.

2) Speed Ratings: There is a test that a speed rated tire has to pass. This is not a "test the tire, then assign the rating" sort of thing. It's a "this tire has this speed rating, so it passed the test" sort of thing.

Among the testing conditions specified are the rated load and the rated inflation pressure. The rated load is the one listed on the sidewall, BUT the rated inflation pressure is 35 or 36 psi for Standard Load (SL) tires and 41 psi for Extra Load (XL) tires. In other words, the rated pressure has nothing to do with what pressure appears on the sidewall. What is written on the sidewall is a MAXIMUM.

However, the load on the tires on a given vehicle and the inflation pressure used for that vehicle are not the same as the test conditions. Therefore the actual speed capability of a tire used in a particular situation may not be the same as the speed rating.

This is an area that is not well explored. While it is known that it is the standing wave that limits the speed capability of a tire (and not the heat being generated), the exact effect of inflation pressure vs load is not well understood - too many variables - except to say that both lower inflation pressures and higher loads reduce the speed capability of a tire.

We also know that there is an upper limit to inflation pressure - the burst pressure. Clearly the burst pressure is dependent on the strength of the materials in the tire's casing. Put another way, the stronger the casing, the higher the burst pressure.

- BUT -

Increased speed also means increased stresses, and therefore a stronger casing will be needed for higher speed ratings. The exact nature of the "stronger casing" is a trade secret for each tire manufacturer - but it is common knowledge that a circumferential overlay on top of the belt greatly enhances the speed capability of a tire (meaning that the sidewall plays very little role in speed ratings)

BTW, the maximum pressure listed on the sidewall of a tire is not a reliable indicator of burst pressure - not to mention that tires degrade over time as does the actual burst pressure. (It has been known for very old tires to burst at normal inflation pressure.)

In addition, overlays of the belt package also decrease a tire footrpint's sensitivity to inflation pressure. In other words, a tire with a cap ply maintains a more uniform pressure distribution over a range of inflation pressures.

When translating the effect of LRR tires into your own mpg readings, it will pay to be up on the topic of speedometer accuracy, or lack thereof, due to tire size differences. Tire Rack (see link below) presented some info that bears consideration, else you make false claims of joyously increased mpg or become suicidal because you lost mpg due to a tire change.

I ran into this some time back checking the FE of my Accord, which, it turned out, has shorter tires than the speedo was calibrated for (namely 205/60R-16). These are factory installed tires ,BTW, but the speedo is calibrated for 205/65R-16 tires. The end result is that I was traveling about 64 mph while indicating 70 and indicating about 110 miles while traveling only 100. Needless to say, I was "Whoo-hooing" my great 31-32 mpg out of a 3.0L V6 while actually getting under 30 mpg.

Well, we're "only" going to get about 70K from the OE Michelins but I will be replacing them with 65 series tires. I contacted Honda, BTW, and they claimed to have no way to recalibrate the car for the shorter tires.. unlike some other mfrs that can reflash the PCM for a variety of tire sizes. The the 65 series tires have a radius about 3/8-in taller and will put the speedo back to a more accurate state, but also drop the rpms by about 75 at 70mph, which could deliver a slight mpg gain.

I have a programmer on my Ford pickup and I measured the tire circumference to the millimeter at my standard pressure, entered that into the programmer and my speedo is deadnutz. As the tires wear, I can remeasure to keep the speedo as accurate as possible. On my other cars, I determine a correction factor as accurately as possible and use that in calculating my true miles traveled.

Tire Tech Information - Tire Rolling Resistance Part 3: Changes to Expect When Switching from Worn-Out to New Tires

More Clarfiying Points:
 

A word of caution: The rolling circumference of a pneumatic tire is about 3% less than the measured circumference.

which may mean the speedometer is calibrated to actual circumference and internally compensates for that 3%. Other vehicles may not do that!

If you look closely at what Tire Rack did, they took a tire with 12/32nds tread depth and compared that to a tire with 2/32nds. That would be 10/32nds difference in radius = 20/32nds in diameter = 0.63" on a diameter of 24.9" or 2.5%. They only got a 1.5% difference in distance traveled!!!

Tread depth differences don't directly translate into circumference differences!

Also, many of the revolutions per mile (rpm) values are CALCULATED values. And take it from someone who used to do those calculations, the formulae may be old and unverified for many, many years, so their accuracy is suspect. Besides, most folks who would do those calculations would think that within 2% is close enough!!

Also, if you do the calculation on the values that Tire Rack has in the artcle, you'll see the diameter values vary from the rpm by 2½ to 3½%.

So use caution when using published rpm and dimensional values!

Not quite sure what you mean here, Capri. Would you clarify, please?

How i measured circumference, by the way, is by marking the tire and the pavement, rolling forward one revolution and measuring the distance on the pavement (garage floor, actually). The programmer allows for increments as small as 1mm. I don't know that the programmer or the truck's PCM does any internal compensating, hence my query above, but I happen to know the designer of the programmer, so I can ask.

The other thing is that tires tend to expand a little from centrifugal force at speed. It caries from tire to tire, I guess, but even I'm not THAT pedantic! If there is a rule of thumb, I'd like to know what it is.

Even more Clarification
 

Jim,

That is an interesting way to measure circumference.

Most folks would have used a tape measure around a freestanding tire - and that was what I was referring to when I made my comment about internal calibration. I can think of several ways of dealing with the tire circumference / speedometer issue - This would be just one of them.

Expansion due to centrifugal forces?

Let me put it this way: I would think that load / inflation pressure effects would be greater than the effect caused by centrifugal forces. I know of no rule of thumb for load / inflation pressure nor one for speed.

Capri: Is that,
"Interesting, that's the dumbest thing I've ever seen!"
or
"Interesting, cool way to do it!" ( : < )

Either way, it's not my idea. It's how the programmer wanted you to find the circumference. Easy to do. I though it was cool. My other method is to measure the loaded radius with the tire inflated to the pressure I will use.

If you have other methods, would love to hear about them!

As to centrifugal forces, a tire engineer told me regarding one particular tire (a big, high profile, 38 inch diameter, 15 inch rim, mudder) that the tire grew in circumference by several mm at high speed (he did not define "high"). I never did get to question him further to see if this was a general phenomenon, or something found just on that tire, or others like it. That's why I asked you about it.

I just check my odometer at a mile post on the highway, then check it again 30 or 40 miles later and see what the discrepancy is.

And the Clarifying continues:
 

Actually, my reaction was "I wouldn't have thought anyone would do it that way, even though that's a pretty good way to do it."

No!! The loaded radius is not the way to do this. BTW, this is called the Static Loaded Radius and it only affects ride height - which is why some find it a useful statistic to have.

Long story, but the short version is that the axle is off center both from the top and the bottom of the tire. The tire kind of hangs from the top and pushes down on the bottom.


This is probably a bias ply tire - and yes, those types of tires will grow. You can see this phenomenon in drag racing - especially Top Fuel where the speeds are high and the tires are exposed.

But we are talking about radial tires with a belt which restricts the growth. In fact, growth of this nature is such a problem for radial tires that higher speed rated tires will have a circumferential overlay which further restricts the growth.

Folks that are into bicycling (as I am) that need to calibrate bike computers will measure this way too (rather than use a tape measure around the circumference)... not that bike computers need to be all that precise, but still the same idea. I usually use chalk on the tread which then leaves a mark on the pavement for several revolutions before becoming too faded, and then measure between the marks.

All tires are subject to the centrifugal force which can make them bulge slightly while rotating. The faster the rotation, the greater the chance of distortion/bulge.

Hi,

I recently got a TireRack.com catalog in the mail and they actually have a blurb on low rolling resistance, and they list three tires that are low(er) rolling resistance:

Michelin "HydroEdge Green X" (UTQG Rating 800 A B)
Goodyear "Assurance Fuel Max" (UTQG rating 580 A A)
Bridgestone "Ecopia EP100" (UTQG rating 400 A B)

Has anybody tried any of these, or have you heard anything about them?

Accuracy of speedometer and odometer? Why not just check them with a GPS?

If you are comparing fuel economy, best to make sure both cars are going the same speed, otherwise, what have you proved? With my car, a one mph error in speed makes a one mpg change. I apply corrections to both speed and odometer when it's important to know.

If you increase tire diameter, fuel economy will usually increase, but it will SEEM to go down unless you correct for guage changes.

/Ernie Rogers

Ernie -

Yeah, I periodically use a GPS correction for my one-size-up-from-stock tires :

http://ecomodder.com/forum/showthrea...ires-2642.html

I apply the correction to my fuel log, so it's like a mini-bonus.

CarloSW2

I contacted Michelin directly a few months ago, and they recommended the Hydroedge.

Another one that looks good is Nokian i3.

What do you think the rolling resistance is on these?
http://thereifixedit.com/wp-content/...skateboard.jpg

I contacted Nokian also, and they said the i3 is good but the H is better.

http://www-nrd.nhtsa.dot.gov/pdf/esv/esv21/09-0300.pdf

Here is some test data on Rolling resistance. I understand that best low rolling resistance tires in that test are:
goodyear integrity and bridgestone potenze RE92 owl?

I find it interesting that the rank order changed slightly depending on which test was run.

I also find it interesting that the Goodyear Integrity and Cooper Discoverer ST-C were tested in 3 different sizes - and that the RRF values were different enough that one of the 3 was in a different grouping.

I have always tought that tire companies do almost all the R&D work on popular sizes. Then they will just scale it down to other sizes and widths and say that they are the same. Maybe that test proves my estimations true?

While I can confirm that tire manufacturers develop tires in a couple of sizes, then scale them up and down as appropriate, I think what the test says is that there is something else going on and you can't compare the rolling resistance of tires of different sizes.

I'm surprised no one has posted this in this thread:

http://www.energy.ca.gov/transportat...%20Testing.pdf

It's a study done for the California Energy Commission. Not only does it test various tires for rolling resistance, it also studies the effect tire size has on rolling resistance. This confirms that different sizes of otherwise identical tires have different values - enough that you can't reliably compare tires of different sizes.

I ran a regression analysis on the data and developed an equation so the differences in tire size could be compared, but the R-squared value wasn't all that great: 66%

Yes I also meant that popular sizes. Usually this means tires that are normally used as factory size tires on cars. There 3-5 popular sizes on different size cars. Other sizes are then scaled like you confirmed. This gived me a nice idea and lets see how things start to develop.

That report was superb. If you have more similar "open" reports on your sleeve please post ;).

I know that in some places in Europe, only tires approved by the vehicle manufacturer are allowed to be applied - even as replacements.

That is definitely not true in the US. There are whole lines of tires - 30 to 40 different sizes, that are designed off a couple of prototypes - and that was what I was referring to.

- AND -

It is pretty universal that any OE tire is unique to itself. The vehicle manufacturer decides what the performance specs are supposed to be, and the tire manufacturer complies. If the tire manufacturer refuses to go along, te vehicle manufacturer will find some tire manufacturer who will.

I believe I've been able to identify at least one of those variables which change in a non-scalar way when tires are scaled up or down for size. For example, the legendary Bridgestone B381 185/70-14 tires have a 5.0" tread width, while the 185/65-14 version of the same tire has a 5.4" tread width. If my math is correct, that's an 8% increase in tread width, which would increase the size of the contact patch and also increase rolling resistance.

While looking at other tires, it seems the tread width of the same tire between different sizes goes up or down almost arbitrarily depending on the brand.

Tirerack is pretty good about giving detailed specs about tires.

JMac

contact patch size does not change
 

Sorry, but that is an old wive's tale:

Fact or Fiction? Tire contact patch and air pressure.

If you want to assume that for the purposes of analysis, go ahead. Just be sure you don't draw any conclusions where that is a vital piece.

Sorry to dredge up an old thread, but beyond tire retailers saying whether a tire is considered LRR or not, has that law actually done anything?

I can find no rating data on LRR tires and am strongly considered Bridgestone Ecopia ep422 PLUS's for the volts front tires (don't ask) over the stock crapola

But I have no idea what tire is the most efficient in the goofy 215/17's that are on the car.

Some folks claim an extra 6 miles range using the ep422 plus (not the regular non plus version) over stock but there is nothing to support or validate that claim.

Ah well. I am told the euro specs should not be used to compare the same brand tires here because the same model of tire can be different in our country as compared to europe, ah well.